Protesters in Washington in 2011 were already demonstrating against the tar sands pipeline. Environmentalists say extracting crude from sand emits three times more carbon than conventional oil production, contributing to global warming.

Conservation groups have added allies and opened a new battlefront against pipeline expansion projects that will bring more Canadian tar sands crude oil through the Midwest.

A coalition of 29 groups and former public officials, along with 36 landowners, petitioned two federal agencies to impose tougher pipeline regulations in advance of proposed upgrades to Enbridge Inc.’s pipelines that carry Canadian oil through Minnesota, Michigan and other states. Coalition leaders said Wednesday their goal in the pipeline fight is to stop Canadian tar sands development.

“It’s mainly about protection of habitat and wildlife, but our issues run all the way to climate change, including the impact of fossil fuels,” said Gary Botzek, executive director of the Minnesota Conservation Federation, an organization of local sportsman groups.

For the past four years, environmental activists have fought a prominent battle against TransCanada’s proposed Keystone XL pipeline through western states to the Gulf of Mexico. Activists say extracting crude oil from tar sands increases greenhouse gases that cause global warming. Keystone XL has provoked protests at the White House, where President Obama is weighing whether to grant the project a permit to cross the U.S. border.

The coalition led by the National Wildlife Federation is concerned about Midwestern pipelines that already carry the same heavy oil. One line runs through Clearbrook, Minn., and across northern Minnesota to Superior, Wis. From there, it connects to other Midwestern pipelines. The system is owned by Enbridge of Calgary.

Larry Springer, a spokesman for Enbridge, said the company opposes the petition for new regulations.

“This oil has been transported through pipelines safely for decades,” he said.

Botzek said this is the first time the Minnesota conservation group has opposed pipelines. He said the coalition wants to halt expansion of Enbridge’s system that carries Canadian crude, but is not advocating shutting down the existing lines.

Its petition to the U.S. Environmental Protection Agency and the U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration seeks new regulations to address heavy-oil pipeline ruptures, including a requirement to shut them down at early signs of possible leaks. Other proposed regulations focus on emergency response and disclosure of what pipelines carry.

Enbridge’s Springer said the oil industry already is working with regulators on several issues raised in the regulatory petition, including revised emergency response and studies of the corrosiveness of the crude oil. “A lot of the issues they raise are being studied,” he added. “A lot of the issues have been dealt with.”

The U.S. pipeline safety administration, in an e-mailed statement, said it is working to better understand whether the diluted heavy oil mixture sent through pipelines poses an increased risk of release. As part of the work, the National Academy of Sciences is conducting a study due in July. The EPA did not have an immediate comment on the petition.

Besides petitioning for tougher regulations, the wildlife federation said it’s building a coalition to oppose an amended “presidential permit’’ that would allow more tar sands oil to cross the U.S. border via Enbridge’s upgraded Alberta Clipper pipeline, which crosses Minnesota. The U.S. State Department recently began an environmental study of the proposal.

The project, which includes $40 million for pumping stations in Minnesota, is part of $6 billion in pipeline upgrades in the United States and Canada that Enbridge announced last year. The 1,000-mile Alberta Clipper line, completed in 2010, carries thick oil, called bitumen, extracted in northern Alberta. That oil must be diluted with light petroleum products so it can move through pipe.

In 2010, a ruptured Enbridge pipeline in Michigan sent diluted bitumen into the Kalamazoo River, with some oil sinking to the bottom, complicating the cleanup, said Beth Wallace of the Wildlife Federation. “This disaster should have been a wake-up call to industry, regulators and public officials,” Wallace said.

But Springer said the oil sank because it attached itself to sediment in the water. “It is something that needs to be studied,” he said, “but it is not an issue related specifically to diluted bitumen.”

With pipeline capacity unable to keep up with the oil booms in North Dakota and Canada, many oil producers have turned to railroad tank cars to ship crude oil. But Jim Murphy, senior counsel for the wildlife federation, said the coalition doesn’t support crude-by-rail as an alternative to pipelines.

In a sign that rail also carries risk, a Canadian Pacific train with a mixed load of crude oil and other cargo derailed Wednesday morning near Parkers Prairie, Minn. No one was hurt, and crews were cleaning up the estimated 20,000 gallons of crude oil that spilled from one tank car.

David Shaffer • 612-673-7090 Twitter: @ShafferStrib

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In Bradshaw, Neb., earlier this month, this sign made its point about the Keystone XL pipeline that could run through this field.